For example, development has advanced on a probe memory in which a recording medium is displaced (or driven) along a recording surface of the recording medium with respect to a probe array including a plurality of probes and data is recorded onto the recording medium or the data recorded on the recording medium is reproduced by using each of a plurality of probes. Instead of displacing the recording medium, the probe array may be displaced. In general, in order to bring a recording/reproducing head such as a probe in contact with the recording medium with a certain force, or in order to keep them at a certain distance, a spacer is provided between a substrate provided with the recording/reproducing head and a substrate on which the recording medium is mounted.
Moreover, the use of the spacer is not limited to the aforementioned probe memory. For example, as disclosed in a patent document 1, a spherical spacer is provided between one pair of electrode substrates for applying a voltage to a liquid crystal. Moreover, a patent document 2 discloses an example in which particulates are contained in an adhesive layer between a plurality of substrates which constitute an optical recording medium.    Patent document 1: Japanese Patent Application Laying Open NO. 2002-49041    Patent document 2: Japanese Patent Application Laying Open NO. 2001-195784